The present invention relates to an improvement in an electromagnetic pump for, e.g., fuel supply of an automobile.
An electromagnetic pump to be used as an automobile fuel supply pump or the like is desired to have a simple structure not requiring high part machining and assembly accuracies and to stably perform a pump operation.
Conventionally, the present inventors have proposed, in, e.g., Japanese Utility Model Laid-Open Nos. 61-70581, 61-76172, and 1-99981, a portable electromagnetic pump in which the arrangement of an individual portion is simplified to decrease the number of constituting parts, the reliability in machining, assembly, and operation of each portion is improved, and the entire pump can be made small in size and light in weight at low cost. That is, in this portable electromagnetic pump, a pump housing is constituted by a substantially cup-like housing main body and a cover member for closing the opening end of the housing main body. A resin coil bobbin for winding an excitation coil arranged around a sleeve member for housing a plunger, a printed circuit board stacked outside one flange of the bobbin with a predetermined interval therebetween to mount various types of electronic parts including a transistor, and a holder stacked outside the printed circuit board with a predetermined interval therebetween are sequentially stacked and housed in the pump housing and biased against the cover member by a biasing means such as a leaf spring provided on the housing main body bottom portion side. As a result, variations in dimensions between the housed members are absorbed to realize a stable assembly state.
In the above conventional structure, the transistor arranged close to the printed circuit board is mounted on the circuit board while being inserted together with a heat radiation plate into a stud formed on the coil bobbin and is held by setting the holder. Various types of electronic parts such as a surge absorber mounted on the circuit board are laterally assembled on the circuit board and fixed by soldering or the like with their lead portions being bent. In this conventional structure, however, the assembly of circuit parts is cumbersome and complex and requires a long assembly time. Therefore, this structure is still unsatisfactory to realize a low manufacturing cost. In particular, the assembly operations of each pump portion including the assembly of a circuit part of this type onto the circuit board are desired to be automated as much as possible.
Another problem of the above conventional structure is a mounting efficiency of mounting the circuit parts described above onto the circuit board. That is, in the conventional structure, upon assembly of the circuit parts onto the circuit board, these circuit parts are laterally arranged on the circuit board with their lead wires being bent so as to minimize the mounting space on the printed circuit board, thereby decreasing the size of the pump. This assembly state, however, poses a problems in terms of assembly efficiency and does not efficiently use the mounting surface of the circuit board. In consideration of the fact that to increase the length of a lead wire to mount each part on the circuit board poses a problem in assembly space or a vibration resistance, a lead wire having a minimum length may be vertically inserted into the circuit board to mount a circuit part. In this case, however, in accordance with the type of circuit part, a lead insertion hole formed in the circuit board is closed to disable degassing upon soldering, thereby, easily leading to a connection failure. Also, this assembly is still unsatisfactory in terms of a vibration resistance.